No Signal hoping its graphics card?

I am hoping some one can shed some light into my world. OK heres my problem, My computer kept going No signal when it was in high use playing games like starcraft2 or watching web videos, at first it was once every two weeks, then it continued to get worse and worse till it was everyday, its been going on for a few months,about 50 percent of the time i could still hear my game or movie still running so i was thinking graphics card, and then when it started getting really bad i tried switching monitors to a smaller one and it worked almost 100% better even the temp inside ran cooler after very high use( wanted to make sure things was going better even on the extreme chance. So for about a week and half it worked great then it did a nose dive and the computer turns on but i no longer see the activity or power light come on but there is power flowing to the computer and drives and fans and lights on the mother board come on. I spent pretty much all i could on a graphics card thinking since the monitor switch worked that it was going to be the graphics card and that it was only a matter of time before it would go kaboom on that monitor too. But since that point and waiting on my graphics card to come i read that it could be the cpu or motherboard or powersupply but not a lot of details if thats what outcome was for the people who had a similar problem so good news is welcomed lol and will accept bad news too, also since the summer i keep a house hold fan on my computer and clean it our regularly cause of up to this point to play games like starcraft2 seemed at first ok but then needed the extra circulation and it worked, my cpu and my graphics card seemed to be warm the graphics card was warmer i think than the cpu but after the computer was off the graphics card seemed to cool off faster. my computer specs as best i can get them was asus l1n64-sli ws with anthlon 64fx-72 2 gb ram 500w power supply radeon x1950 pro , cant remember the rest at the moment but if you need it i can find out the rest thanks for any help

I would guess you are over-heating the GPU. Does it happen when it is just running a screen-saver? Does the fan run up to speed? Is the air from the power supply hot, warm, or cool? What happens if you leave the cover off the PC? Are there plenty of case fans - you should have at least one and they should blow into the case. The only fan that should blow out is the power supply (positive pressure configuration).

If something as simple as leaning the cover off makes the problem go away, add a case fan, or a slot fan.

I havent checked thermal paste because i am not sure exactly what i would have to do cause i havent had to do it before but in my search i have read a little on it. I do have the case open and has been since summer with fan blowing towards it plus clean it out with air regularly, since the last summer it was getting a little over heated usually only when i played my game and or watching tons of videos, thought then the video card was going but it happen only like once a week and if you rebooted after a few secs it would be fine for a bit, but after it worked fine and even cooler i thought maybe it was the just the graphics card not being able to handle a bigger monitor at 22 or 24 inch viewsonic cause my parents accer 18 was really running great and also i was having a driver issue with the win vista and the x1950 pro. Pretty much up to the point where the computer wouldnt even come on i thought it was like 80% chance it was the gpu now that activity light and power light stop showing up when i hit power i am fearing its the worst and that the motherboard or the cpu is fried.

One step at a time! You will have a hard time getting to the bottom of any problem if you consider too many problems at once. I asked you some questions to clarify the problem; they were not random. Let me explain my thinking process so we can find you a solution.

Step 1: Understand The Problem Sure, we see the symptom of the problem ( a blank screen ), but the problem is the cause. So we look at the symptom, and say, "What must be true for the video adapter to be working?" We can eliminate power-management and screen savers because you hear your game (the system is not inactive). Now we are focused on the hardware (graphics card). The most common cause of failure is heat, and the symptom of an over-heated GPU is the symptom we see here! The more you work it, the hotter it gets, until it finally is beyond it's designed operating temperature. The problem involves more than just a graphics card. If the internal temperatures of your system case are not low enough, then the fan on the graphics card is blowing hot air on it. This may be enough when it is not being pushed, but start a game, the heat goes up, the air being blown on it is not cool enough, and POW -- lights out! There are lots of ways to solve heat issues. I want to help you find the best solution, thus all the questions.

If I had your machine on my bench, I would remove the cover, and power it up to verify that the fans are spinning, and not making noise (an indication that they are not rung up to speed), I would put my hand over the exhaust fan on the Power supply to verify that air is flowing, and it is not excessively hot. Why the power supply? Because it produces the most heat in your system, and if it is not moving it's heat away from the system interior, other components will over-heat; it has the only fans that direct air out of the system.

Once I saw that the power supply was moving plenty of cool air, I would hold a finger on the heat-sink of the GPU. If I could not hold it there, it is too hot, if not, the thermal compound may need to be replaced (the heat is not being transfered from the GPU to the heat-sink). I always use silver-based thermal compound because it does not dry up like silicon based compounds, and it transfers heat better. But that is getting the horse before the cart. Let's gather and post some information so we can work the problem one step at a time.

well i got the video card installed it , no luck, got the thermal paste cleaned off and new paste put on the cpu , reset the cmos and nothing. Its wierd it has random times it shuts off, i thought i had it fixed cause it ran for 45 mins after i got the video card and thermal paste put on and then it started shutting down again. then wouldnt start and then it ran half way to windows then stopped then went on enought for me to install the new drivers and wouldnt reboot, then got it back on for five mins then wouldnt start up till the following night at midnight. Nothing special happening inbetween so probably no longer a video card monitor thread when redoing the paste on the cpu i had my brother who builds them help me out and looked at the cpu and nothing phyiscal looked wrong with it, if it was my motherboard wouldn't it be more at certain points or if it was the cpu would it not just not work or work slow? while clearing the cmos and such i was able to turn it on and had it running and playing starcraft 2 for half hour before it shut off and the speed was really good. The computer it self before the game seemed normal and again my system seemed to run cooler than before , but did notice the heat sink( or the big metal plate) on my mother board was really hot to touch could it be my powersupply is providing too much or maybe not working properly or would you say my mother board or cpu is almost done?

PC power supplies are switch mode supplies which means they will not put out too much power. They will put out what's needed.
Can your brother not lend you a spare power supply to test with?
Also, closely examine the capacitors on your motherboard to see if any have domed up or are leaking. If you find any, they will need to be replaced.

You're probably barking up the wrong tree. The CPU (Central Processing Unit) is working if, as you say, you can hear sounds when the video goes out. The GPU (Graphics Processing Unit is what you should be looking at. It is part of the Graphics card. You could try something like the Accelero X2 to cool it better, or the ATI Tool (http://download.cnet.com/ATITool/3000-2094_4-10518322.html) to crank up the fan and monitor the heat. DON'T USE THE ATI TOOL TO OVER-CLOCK YOUR GPU!!! If you do, you will create more heat!!!

i have already swapped out the video card for a radeon hd 5670, but it didnt do anything much, we swapped out the video card and put new thermal compound on had it running and then still it would shut off before bios could load and after it went through and just before windows and after windows. i keep a big fan on it constantly and it kept shutting down. And then for some reason it decide to run for a bit in the last few days and i downloaded HWMonitor to see if i could see some overheating issues and the highest issue for heat was cpu which ranged from 59-77 degrees celcius depending if i play a game or not but outside a game it stayed stable at 60. the only weird thing i seen was my -12 voltage was -14.7 to -14.98 which i am pretty sure in lower voltages thats quite a bit out. what systems does the -12 voltages affect?